Circular slide-rule.



i). W. BRUNTQN. UIRGUMR'SLIDB RULE.

APPLIGATISH EIL 2D Nw, 13, 1915,

` Patentad Mar. 25," 1913.

ll' l WHA/5555s Unrrun srnrus PATENT OFFICE.

DAVID W. BRUNTO'N, 0F DENVER. COLORADO.

CIRCULAR SLIDE-RULE.

Tor/,ZZ whom t may; concern:

Be it known that I, DAvn) W. BRUN'rO'N, a citizen of the United States, residing at Denver,in the county of Denver' and- State of Colorado, have invented a certain new and useful Improvement in Circular Slide- Rules, of which the following is a full, clear, and exact description.

The object. of this invent-ion is to prov/ide a convenient. and efficient form of calculator, in the nature of ya circular slide rule. by means of which mathematical problems may be readily solved by the mechanical use of a coi'nbination of logarithmic scales.y

The ordinary' or Mannheim slide rule has proven itself to be a most useful instrument for many of the` calculations required in engineering and ni chanical work, but its length makes it exceedingly inconvenient for pocketuse.

Numerous attempts have been made to manufzucture a circular slide rule which would be as convenient t use and at the same time easily carried in the pocket. Many of these circular slide rules are marvels of ingenuity and good workmanship, but all of them with which I am familiar lack one of the most useful features of the linear slide rule, namely, the combination of the. 'two sets of logarithn'iie graduations, one. double the scale of the other, whereby, for example, the square. root may be extracted or a number squared by merely jumping from one scale to the other.

Most of the calculations which engineers and mechanics have to make, involve at .some stage the necessity for obtaining the area of a circle when its radius, its diameter, or its circumference is known. This operation is performed with such wonderful celerity on the ordinary slide rule that all of the circular slide rules no matter' how ingeuiously constructed, have failed to come into very general use, and this because they carry certain scale's which while extremely use-ful for many purposes, are` not as convenient forncalculations involving the extraction of the square root or the squaring of numbers as the linear slide rule.

Inrising the ordinary linear slide rule, calculations are nearly always made on the A and B double scales instead of on the C and D single Scales, because on the latter the result is very apt to run off the scale.

By the present invention it is sought to combine all of the advantages of the linear Specification of Letters Patent.

Application led November 13, 1912.

Patented Mar. 25,1913.

Serial No. 731,217.

slide rule without its inconvenient length, and the compactness and portability of the circular slide rule, with an endless runner.

The invention consists of a circular slide rule, comprising a two-circle frame having a runner mounted in and between its parts, and a central cursor, containing -also by preference in its mounting a magnifying glass, the frame parts and the runner being suitably graduated, and the face covered by a glass, as I will proceed now more particularly to explain and then claim.

ln the accom] )anying drawings, illustrating the invention, in the several figures of which like parts are similarly designated, Figure 1 is a top plan view and Fig. 2 is a bottom plan view of a preferred construction. Fig. 3 is a cross-section on a larger scale illustrating the structural details of my circular slide rule.

It is to be noted that the graduations on Fig. l are merely indicative or conventionall representations of the A-B and C-D as well as the sines and tangents scales that are to be used upon theI instrument.

The frame comprises an outer circular plate l and an inner circular plate 2 in concentric arrangement, and these two parts are spaced apart' to receive a runner 3, and are connected by one or more -bridges -l which l span the runner space or runway. A ring may be applied to the bridge for convenience in carrying the instrument. The adjacent edges of the plates l and '2 are rabbeted to receive the` runner 3 which is coniplementally rabbeted.' This runner is made as an annulus and fitted between'the plates l and Q and lies in the same plane. An annular back-plate (3 is screwed or otherwise fitted to the back of the runner and it is of a Width suiiicient to overlap the adiacent edges of the frame parts l and 2, so-

as to hold the runner in place in the frame. This back-plate (3 is provided with a depending flange or other rearward extension 7, preferably provided with a knurled or milled edge S or other finger-hold to enable the operator to turn the runner in the runway aiforded by the rabbeted edges of the frame plates l and Q. Within a central holeA in the frame is located a cylindrical housing` or casing 9 having a face flange 10 which overlaps the adjacent edge of plate 2 to hold said casing in position. To this flange 10 is affixed a cursor 'Il overlying the face of the instrument, and within the casing is lie suitably mounted a magnifying glass 1:2.' The casing@ is provided with an eXteriorly arranged finger-hold 15%, here shown as :i knurled ring, byiwhicli .it may be turned, and which abuts againstthe baclt of the frame part or plate :2A to hold the casing inv position in the frame. y

The outer plate 1 `may have a raised 'rim 14c`on a level 'with 'the tia/nge 10 and these two support a glass or other transparent face plate 15, 'which may be engaged. by a bezel 16 which in turn engages-the outer plate 1. Thiselevated :tace-platei-leaves a space between itself and the frame parts anfd runner for the travel of the cursor.

In the preferred form, th'e instrument wil.

jb'esupplied lwith the double sets oit' loga- 'rit'hinicscales commonly known as the A-B and C-D scales exactly as used on the ordinary Mannheim linear slide rule. The combination. of two sets ofv graduations, one double the scale of the other, is extremely useful in making calculations 'where it necessary at some stage of the process to eX tract the square root, since it is only necessary to jump from one scale to the other to extract the square root, or reverse the reading to square anumber. So fai* as I am aware, the circular slide rules have carried only one set of scales and were incapable of extracting the square root or squaring a number in this manner.

In using the ordinary linear .sl-ide rule, calculations are nearly always made on the A-B doublescales instead of on the C-D single scales, and for the reason that on the latter the result is Very apt to run off the scale. Ina circular slide rule, such as mine, the runner being endless, the result never runs ed, and consequently the ordinary operations of multiplication and division may be 'more conveniently performed on the single scales than on the double scales, and as a result, l am enabled to make a small and convenient pocket instrument of about three inches in diameter, with which calculations-may be made with the same accuracy as is ordinarily obtained upon a fifteen inch linear rule.

lt is tobe' noted that my rule carries an endless runner on an entirely unobstructed face, and hence the instrument really combines all ofthe advantages of-both circular Iand linear rules."

The circular housing carrying the cursor is utilized to receive the magnifying glass,v

which will be found convenient in reading *graduations on scales, surveying instruments and for examining mineral and other specimensl' As shown, the magnifying glass is held between the inner proyection of the 'flange 10 and a suitable retaining ring 17,

although other means may lbe employed to hold the glass in place.

indicated in Fig. 3, the scales may be applied to the instrument by means of added material 1S, such paper, Celluloid, or other suitable vehicle, although the scales may be cut in the. metal of the parts, or otherwise suitably applied to the instrument.

While the circi'ilar linger-holds are preferred, it is to beunderstood that the invention is not limited to the use of any par ticular kind of means for turning the runner or the cursor l'1olde1..

lllhatl claim is:-.

1. i circular slide rule, having a two-part frame, the parts of which are concentricnnd separated a runway, and one or more bridges spanning the runway and rigidly connecting the parts, and an ei'idlessrunner mounted in said runway and provided with a finger-hold.

2. A circular slide rule, having a frame made with twoconcentric parts which are separated by a runway, and one or more bridges spanning the runway and rigidly connecting the parts, an endless runner mounted in said runway and. provided with a ingenhold, a housing centrally arranged within the frame and provided with a iingerhold, and a cursor mounted on said housing.

3. A circular slide rule, having a frame comprising two circular plates separated by a runway, and one or more bridges spanning the runway and rigidly connecting said plates, an endless runner mounted in said 4runway and provided with a finger-hold, a housing centrally arranged within the frame and provided with a finger-hold, a cursor carried by saidhousing, the faces of the frame plates and runner being in the same plane and provided with appropriate logarithmic scales, and a face cover mounte over and inclosiiig the scales.

4f. A circular slide rule, `having a framev provided with concentric plates, the adjacent edges of which are rabbeted, a circular ruimer mounted upon said rabbeted edges, and a back-plate provided with a fingerhold and attached to the back of the runner with its edges overlapping the adjacent edges of the frame plates.

5. A 'circular slide rule, having a frame made with a central 'opening provided with a flanged housing, the fiange overlying the edge of the opening and provided with a cursor, and said housing extending back of the frame and provided with a ingenhold which additionally holds `the housing in place.

6. A circular slide rule, composed of a frame having two concentric plates spaced apart. and united by a bridge or bridges, a' runner vmounted in the space between the plates and provided with means to turn it, and a cursor mounted centrally within the frame, the frame plates and runner carrying one single set and one double set of logarithnr'ic scales arranged so as to permit the automatic extraction oflsquare roots, squar- 1ng numbers as well as for other purposes.

7. A circular slide rule, having a t-wo- 4'part frame, `the parts of which are concentric and separatedby a runway and bridged 4together over the runway, and an endless runner mounted in said runway and provided Witli a depending flange forming a finger-hold for operating the runner.

8. A circular slide rule, having a frame made with two concentric parts separated by a runway and bridged together over the runway, v v

said runway and provided with a dependan endless runner mounted in DAVID w. BRUNTON.

' Vitnesses:

ROBERT K. MoCoRM1cK, H. ELLIS SEALING. 

